Buckets for earth moving equipment, such as excavators, are subject to a high degree of abrasive wear. This wear is particularly pronounced at a leading edge of the bucket, where ground engaging tools such as adaptors and teeth are used to penetrate matter being dug. It is also found at bucket corners and heels, although wear in these areas is not as pronounced as at the leading edge.
In order to prolong the working life of a bucket, and to retain structural strength in the face of this wear, it is common practice to fix replaceable wear members to those parts of the bucket most subject to wear. Traditionally wear members such as teeth, wear strips and heel shrouds have been welded into place on a bucket.
Although the welding of wear members to buckets provides a secure means of attachment, it has significant practical difficulties. Replacement of worn members requires the cutting out of the worn member, and the fitting and re-welding of a new member in its place. Such metal-working operations require specialised equipment and trained boilermakers.
Where the bucket is being employed remotely, the removal of the bucket, transportation to a suitable workshop, replacement of the worn member and transportation back to the remote location can result in a significant time delay, and thus a loss of production. As excavators are often highly expensive, the underutilisation caused by the need for bucket repairs has a significant economic consequence.
In response to this problem, methods of mechanically attaching ground engaging tools to the leading edge of the bucket have been developed. An example of such a method is disclosed in the international patent application published as number WO02/12642, in the name of a predecessor of the present applicant.
Generally, known methods of mechanically attaching ground engaging tools to a bucket leading edge involve providing the ground engaging tool with a channel which locates about the bucket leading edge, and then clamping or bolting the ground engaging tool in a particular position along the bucket edge.
The geometry of this arrangement greatly assists in the attachment of ground engaging tools. The principle forces to which the tools are subjected are shear forces and compressive forces, and generally speaking these forces are transmitted directly to the bucket leading edge, rather than through the clamp or bolt being used. The mechanical attachment is thus only really required to prevent lateral movement of the tool along the bucket edge, or the pulling away of the tool from the bucket edge.
There have been relatively few attempts to provide a mechanical attachment of heel shrouds to excavator buckets. There would appear to be two reasons for this. Firstly, the rate of wear of heel shrouds is less than that of ground engaging tools, and thus the economic advantage of mechanical attachment, whilst significant, is not as great as for ground engaging tools at the bucket leading edge. Secondly, and perhaps more significantly, the geometry of heel shroud attachment is much less promising than at the bucket leading edge.
Heel shrouds must be mounted around corners or heels of the bucket. As such, there is no lip for them to clamp around. In other words, the angle included by a heel shroud is in the order of 90°, as opposed to an included angle of about 20° typical for ground engaging tools. Any force acting on the heel shroud, except for a direct compressive force, will act directly on the attachment system on at least one face. This places significant stress upon the attachment system. To date, therefore, welding has proved the only suitable method of attachment.
Research by the applicant has revealed an attempt to overcome this problem by bolting of heel shrouds to bucket corners and heels. This technique has several drawbacks. Firstly, the drilling of bolt holes within the bucket can reduce the bucket strength. Secondly, there is a tendency for bolts to deform under load. When this occurs, it can be impossible to remove a bolt using normal mechanical tools, and it may be necessary to cut the bolt from the bucket. This, of course, eliminates any advantage gained by the use of such bolts.
The present invention seeks to provide a means of mechanically attaching a heel shroud to an excavator bucket which does not require bolting through the bucket walls.